The need for degassification of liquids is encountered in the above-mentioned applications and others which will be recognized by those of skill in the corresponding arts. An application for which the present invention is especially useful is the degassification of potable water for use on a spacecraft.
Prior art liquid degassifiers all provide some form of liquid particle or film break-up to increase liquid surface subject to degassification. The prior art apparatus for the accomplishment of that filming or particlizing has usually been bulky because of tray and baffle use. Also, such prior art apparatus occupies a large fraction of the container tank volume.
Finally, motor drives have been used in some prior art devices (in addition to the usual pump).
The general concept of degassing a liquid or liquid mixture in a partial vacuum is disclosed in U.S. Pat. Nos. 3,517,487 and 3,555,819 (Burnham) as well as in U.S. Pat. No. 2,714,938 (Smith) and various other references, and can be considered known per se.
U.S. Pat. No. 4,007,022, (Schleicher et al.) deaerates a dispersion of PVC in water while Burnham is concerned with deaeration of drilling mud, both more viscous mixtures, than water or the like as so advantageously handled by the invention.
U.S. Pat. No. 2,071,393 (Doherty) concerns deaeration of a relatively viscous mixture, to wit: catsup. A motor drive appears to provide a type of centrifuging action by means of a driven beater arrangement. U.S. Pat. No. 2,041,059 (French), applies teachings very similar to those of Smith to the degassing of milk or cream during pasteurization. U.S. Pat. Nos. 3,358,425 and 4,210,176 (Rodman et al.) accomplish a very similar result for oil purification employing rotating disks for fluid filming.
U.S. Pat. No. 2,064,650 (Emanueli) degasses liquids, particularly oil, by spreading the liquid over a filming structure by centrifugal force (a motor-driven structure).
U.S. Pat. No. 2,020,250 (Stephens) concerns food processing by deaeration to remove odors generated by prior ultra-violet irradiation. Vanes for generating a deaerating surface are provided, the material being processed as it passes over surfaces in a partially evacuated vessel.
In U.S. Pat. No. 1,836,338 (Rodman et al.), spraying of a liquid vertically upward into a partially evacuated vessel is employed for degassing.
Causing a liquid (i.e., oil) to flow in a thin layer over an elongated path at less than atmospheric pressure for degassing and water vapor removal appears to be the essence of the U.S. Pat. No. 3,789,579 (El Hindi).
The special problem of degassification of a high viscosity liquid (e.g., viscose) in a vacuum tank as the liquid passes over baffles intended to cause a filming action, is described in Elliott et al. U.S. Pat. No. 3,368,330.
U.S. Pat. No. 3,325,974 (Griffin), provides the basic function of drilling mud degassing at sub-atmospheric pressure by passing the mud over baffle surfaces as in Burnham patents aforementioned.
U.S. Pat. No. 1,598,787 (Shields) degasses water and soft drinks, etc., to increase affinity for desolving CO.sub.2 for carbonation. A series of "pans" provides for breaking up the liquid in the vacuum chamber.
U.S. Pat. No. 1,457,153 (Elliott), degasses steam boiler feed water in a vacuum vessel relying on the "violent ebullition of flashing action" during injection into the vessel.
U.S. Pat. No. 2,540,390 (Gorgerat et al.) and Canadian Pat. No. 653,008 (Anderson) are further examples of spray methods for increasing the liquid degassing surface, by gravity liquid fall and force nozzle over a guiding core, respectively.
Other drilling mud degassers are disclosed in U.S. Pat. Nos. 3,831,352 (Parcels) and 3,358,425 and 3,481,113, Parcels having a break-up impeller and all comprising baffle structures in a vacuum vessel.
Canadian Pat. No. 653,008 (Anderson) undertakes to constrain the filming aperture of the liquid between concentric conical surfaces, but thereafter permits liquid flow over one conical surface such that the liquid is exposed to the vacuum environment on one surface only.
U.S. Pat. No. 2,979,156 (Sebald), appears to employ liquid spray degassing in a vacuum vessel with particular attention to pressure equalization to minimize the vacuum pumping effort required.
Most of the foregoing prior art references include flow-path baffle or tray arrangements for increasing the liquid or mixture exposed surface in a vacuum vessel, except where conventional spray apparatus is employed. The prior art does not appear to include the concept of cascading the liquid in thim films within a vacuum vessel free of any filming baffle or other guiding structure.
It will be seen that truly thin film liquid formations for optimum degassing efficiency are not provided in the prior art. Moreover, wherever a liquid flow over a surface is relied upon to obtain a liquid film, only one surface of the film is exposed to degassification force (vacuum, for example).
Liquid sprays do not provide sufficiently high liquid surface exposure for optimum degassification, and "mud" or other liquid/solid mixtures are obviously not degassable in analogous structures and by analogous methods vis-a-vis, the degassification of water and other liquids of relatively low viscosity.
The manner in which the invention deals with the disadvantages and inadequacies of the prior art will be understood as this specification proceeds.